Status of mature and old-growth forests in the Pacific Northwest

Conserv Biol. 2006 Apr;20(2):363-74. doi: 10.1111/j.1523-1739.2006.00384.x.


Nearly 10 million ha of federal lands in the Pacific Northwest have been managed under the Northwest Forest Plan since 1994. The plan reduced logging levels by 80%; only recently, however have inventories on status and condition of mature and old-growth forests become available. Our objectives were to (1) determine the areal extent of old (> 150 years) and mature (50-150 years) conifer forests based on 2000 Landsat 7 ETM+ imagery, (2) examine levels of protection, (3) determine the degree of additional protection afforded to old and mature conifer forests if late-successional reserves (LSRs) and inventoried roadless areas (IRAs) were fully protected, and (4) review management options to achieve greater protection of older forests. The historical extent of old-growth forest in the Pacific Northwest was roughly two-thirds (16,672,976 ha) of the total land area. Since the time of European settlement, approximately 72% of the original old-growth conifer forest has been lost, largely through logging and other developments. Of the remaining old growth, the Central and Southern Cascades and Klamath-Siskiyou account for nearly half Mature conifer area (4,758,596 ha) nearly equaled the amount of old conifer More than 78% of the old growth and 50% of mature forest were located on public lands. Approximately one-quarter (1,201,622 ha) of the old-growth conifer (or 7% of the historical old-growth area) was classified as GAP status 1 (strictly protected) or GAP status 2 (moderately protected). The total area of LSRs was slightly more than 3 million ha, approximately 36% (1,073,299 ha) of which contained old-growth conifer forest. Combined old and mature conifer within LSRs was approximately 59% of the total LSR area. The total amount of IRA for the Pacific Northwest was approximately 1,563,370 ha; of this, 526,912 ha (34%) was old growth. The combined area of old-growth conifer forest accounted for by protected areas (GAP 1 and 2), LSRs, and IRAs was 2,401,780 ha, which accounts for 66% of the old-growth conifer forests on public land, 51% of the old conifer in the region, and 14% of the amount that occurred historically. Outside these land designations, an additional 1,240,271 ha of old growth are on other public land and another 1,023,392 ha are on private lands throughout the Pacific Northwest. Our results indicate the need to periodically monitor status and condition of older forests and strengthen protections of old growth in the region.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Conservation of Natural Resources / methods*
  • Forestry / legislation & jurisprudence*
  • Forestry / organization & administration*
  • Northwestern United States
  • Trees*